The Church of England will face a battle in Parliament and the prospect of
legal challenges if it fails to approve women bishops on Tuesday, MPs said
on Monday.

Special legal privileges and even its position as the established Church could be called into question if the General Synod rejected the plan, they warned.

The Synod will vote on whether to admit women to the episcopacy at a special sitting in London. Despite strong support throughout the Church for the move, the outcome was described as on a “knife-edge” because of the need to secure two thirds support in all three of its branches: bishops, clergy and laity.

The outgoing Archbishop of Canterbury, Dr Rowan Williams, is pinning hopes for his legacy on the success of the vote. His successor, Justin Welby, the Bishop of Durham, is also due to make an impassioned plea in favour during the debate.

The outcome could hang on a handful of votes among the laity, with a number thought to be still undecided.

Under the current plans, traditionalists in the Anglo-Catholic and conservative evangelical strands of the Church, who object to women bishops on theological grounds, would be able to opt out of the authority of a woman bishop. An alternative male bishop would be chosen “in a manner which respects” their beliefs. The option is likely to be taken up by about 900 of the Church’s 13,000 parishes.

Opponents say the compromise does not offer them enough safeguards but calls were growing for them to abstain rather than vote against in order to allow the measure to go forward, ending a tortuous, 12-year process.

MPs, who must approve any Synod decision before it receives Royal Assent, warned that a failure to approve the proposal could undermine the Church of England’s position as the established Church. Chris Bryant, the Labour MP and a former Anglican priest, said the legislation would face a “rough ride” in Parliament if there were any further concessions to traditionalists. “If the legislation leans too far towards the traditionalist that won’t please the Commons and the legislation would have trouble,” he said.

“There are quite a few of us who think that the way this is leaning is entrenching forever a religious apartheid within the Church of England.”

He added that a rejection would “undoubtedly undermine” support for aspects of establishment, including bishops in the Lords and the role of Parliament approving Church laws.

Frank Field, a former Labour minister who sits on the parliamentary ecclesiastical committee, said that in the event of a no vote, he would table a motion to remove the Church’s special exemptions from equality laws.

“It would mean that they couldn’t continue to discriminate against women,” he said.

Susie Leafe, of the campaign group “Proper Provision” that represents women opposed to women bishops, said a failure to include robust safeguards for traditionalists would lead to a slow haemorrhaging of evangelicals.

“It won’t be the death of Christianity,” she said. “The Church will grow, it just won’t be the Church of England.”